High-resolution Ultrasonography and Magnetic Resonance Imaging of Ulnar Nerve Neuropathy Beyond the Guyon Tunnel: Examination

Purpose or Learning Objective: Ulnar nerve (UN) neuropathy is the second most common upper limb neuropathy with an incidence of ~ 30 per 100,000 person-years. In most cases it affects both motor and sensory axons, leading to a mix of sensitive and motor impairment. Atypical syndromes with selective involvement of the superficial sensory branch (SSB) and deep motor branch (DMB) of UN are found in a minority of patients and may represent a clinical challenge due to unusual symptoms and confounding electrodiagnostic results. We aimed to (1) assess the prevalence of DMB and SSB damage in a consecutive series of patients’ electrophysiologic evidence of UN mononeuropathy; and (2) illustrate ultrasonography (US) and magnetic resonance imaging (MRI) findings and determine the value of these modalities in the diagnostic work-up of these conditions.